Reel mower cutting units are grass mowing machines that are used on golf courses and other turf areas that require grass to be cut very accurately. The cutting units are typically rolled across the surface of the ground by a powered vehicle. These cutting units include a generally cylindrical reel that has a plurality of blades which rotate in close proximity to a bedknife fixed with the frame of the cutting unit. Grass is cut by a shearing action between the bedknife and the rotating blades of the reel. The height at which grass is cut can be adjusted by altering the height at which the cutting unit frame is positioned above the ground surface. The bedknife or reel may be routinely serviced and adjusted to be in proper position such that the grass is cut effectively. Reel mower cutting units provide adjustment mechanisms that allow an operator to adjust the clearance between the reel blades and bedknife.
In the past, some adjustment mechanisms for reel-to-bedknife clearance have included a threaded rod that has a lower end coupled with the bedknife. The rod is supported by a bracket fixed with the cutting unit frame. A nut is threaded onto the rod and is positioned above and in abutment with the bracket. The nut can be tightened or loosened to shift up or down along the rod. The rod is positioned within the coils of a compression spring which biases the rod downwardly for maintaining the nut firmly in abutment against the bracket. The rod shifts up or down with respect to the bracket and cutting unit frame as the nut is turned by the operator. Shifting of the rod causes the bedknife to shift up or down, which adjusts the position of the bedknife with respect to the reel blades. The spring, nut and bracket hold the rod and bedknife in the particular selected position. The spring also serves to take any slack or play out of the linkage that may exist in the connection between the rod and the bedknife, or between the nut, rod and bracket. Slack would allow the bedknife to shift during operation, which could negatively affect cut quality and could cause damage to the reel blades or bedknife if the bedknife shifted upwardly into the reel blades due to this slack. When the bedknife on this type of cutting unit strikes an obstruction the linkage mechanism may allow the bedknife to shift upwardly against the compressive force of the spring as the bedknife strikes the obstruction. When this occurs the bedknife may actually strike one of the rotating reel blades, which can cause undesirable damage or wear to the blade or bedknife.
Another reel-to-bedknife adjustment linkage includes a threaded rod that is coupled with the bedknife for altering the position of the bedknife. The rod is positioned within an opening in a bracket, and a pair of jam nuts are threaded onto the rod on either side of the bracket. These jam nuts can be adjusted to alter the position of the rod and thereby alter the position of the bedknife. Adjustments are made by setting the position of the rod by manipulating the nut on top of the bracket so that the bedknife is in the proper position, and then tightening the lower nut upwardly against the underside of the bracket. Tightening of the lower nut against the bracket can sometimes cause the bedknife to shift slightly from the position set by the upper nut, and can therefore undesirably shift the bedknife slightly from the desired position. Adjustment of the bedknife by the use of jam nuts can be a delicate and time consuming process. This type of adjustment linkage also can include a compression spring that will take slack out of the connection between the threaded rod and bedknife. Many such units do not provide compression springs that take up slack that may develop between the nuts, rod and bracket. Since the jam nuts positively set the position of the rod, the bedknife is generally blocked from shifting upwardly into or against the reel blades when the bedknife strikes an obstruction. This type of adjustment mechanism can be relatively difficult to assemble since the compression spring must be somehow held in a compressed fashion while the linkage is assembled.
Another reel-to-bedknife adjustment mechanism includes a double legged bracket which supports a threaded rod, and a compression spring that abuts one leg of the bracket for removing play from the linkage at both ends of the threaded rod. A nut positioned between the legs of the bracket can be tightened on the threaded rod for further compressing the compression spring to thereby remove the force of the spring from the linkage to allow the linkage to be easily swung out to a service position. This adjustment mechanism is shown in U.S. Pat. No. 6,044,637 assigned to Deere & Company.
Another reel-to-bedknife adjustment mechanism includes a screw adjustment device that can be rotated to tilt the bedknife with respect to the reel. A detent locks the screws and permits accurate incremental adjustment thereof. This mechanism is shown in U.S. Pat. No. 3,680,293 assigned to Toro Manufacturing Corp.
Other examples of reel-to-bedknife adjustment mechanisms are shown in U.S. Pat. No. 4,335,569 assigned to The Toro Company, and U.S. Pat. Nos. 4,606,178 and 4,637,204 assigned to Textron Inc.
Other reel-to-bedknife adjustment mechanisms are offered that an operator can use by turning a knob or wheel attached to a rod that changes the clearance. Some of these adjustment mechanisms may include a detent to help limit rotation of the knob or wheel. For example, The Toro Company offers a dual screw “click” adjustment for bedknife to reel adjustment, or a single hand-controlled knob located at the center of the bedbar. The adjustment knob contains a detent with 0.001 inch (0.025 mm) movement of the bedknife for each indexed position.
The detent on these reel-to-bedknife adjustment mechanisms may include a detent spring mounted to the base of the adjustment mechanism with a screw. The detent spring may engage notches or teeth around the outer circumference of the knob or wheel. However, the screw may become loose during mowing operations, and the screw and detent spring then may drop into the cutting unit or onto the ground. An adjustment mechanism is needed for reel-to-bedknife clearance that provides a detent without a screw for attaching the detent spring.
Additionally, a groove may be provided in the side surface of the adjuster base to help the detent spring stay in alignment with notches or teeth in the outer circumference of the adjuster knob or wheel. However, machining the groove into the side surface of the adjuster base is a costly operation. An adjustment mechanism is needed for reel-to-bedknife clearance that reduces the cost of machining parts.